Leguminosae endemic to the Chaco facing quaternary climate fluctuations

ABSTRACT We investigated the influence of Quaternary climate fluctuations on the current distribution of three species of Leguminosae (Fabaceae) occurring in the Chaco. Potential distribution models of Bauhinia hagenbeckii, Muellera nudiflora and Neltuma rubriflora with a supposed endemism area were generated. The Last Interglacial, Last Glacial Maximum, Holocene Middle and current scenarios were used. The species showed a potential distribution according to the South American biogeographic history regarding the glacier regression and the formation of the Dry Diagonal. The models for each Quaternary event exhibited a tolerable AUC ≥ 0.9 for the validations. The LGM was the event that favoured the current species establishment areas in the Dry Diagonal. Quaternary climatic events were related to the current Leguminosae distribution. Bauhinia hagenbeckii and Neltuma rubriflora present similar areas of environmental suitability. Muellera nudiflora models with areas of environmental suitability were larger for the LIG and Holocene than for areas from other periods. All scenario models (LGM, HM and current scenario) highlighted the potential distribution of the three species concomitant with the glacier regression events and were consistent with the history of formation of South American dry areas.

摘要：本研究探讨了第四纪气候波动对查科（Chaco）地区3种豆科（Leguminosae, Fabaceae）植物当前分布格局的影响。针对*Bauhinia hagenbeckii*、*Muellera nudiflora*及*Neltuma rubriflora*三个物种，我们构建了包含推测特有分布区的潜在分布模型。本研究采用了末次间冰期（Last Interglacial）、末次盛冰期（Last Glacial Maximum）、中全新世及当前气候共4种气候情景。基于南美生物地理历史中冰川退缩与干旱对角带（Dry Diagonal）形成的背景，各物种的潜在分布格局与该历史进程相符。各第四纪事件对应的模型验证结果的曲线下面积（Area Under Curve, AUC）均≥0.9，处于可接受水平。其中，末次盛冰期是助力当前物种在干旱对角带内成功定殖的关键气候事件。第四纪气候事件与豆科植物当前的分布格局密切相关。*Bauhinia hagenbeckii*与*Neltuma rubriflora*的环境适宜区范围较为相似；而*Muellera nudiflora*的环境适宜区在末次间冰期和中全新世情景下的模型结果中，范围大于其他时期。所有情景（末次盛冰期、中全新世及当前情景）的模型均显示，三个物种的潜在分布与冰川退缩事件同步，且与南美干旱区的形成历史一致。